The invention relates to corrugated axial filters, and more particularly, to a fold pattern and orientation facilitating improved structural configurations and ease of manufacturing.
Corrugated axial filters are known in the prior art and are typically used in applications where it is desired to package more filter media in a compact volume than obtainable with radial pleated filters. The corrugated axial filter enables reduction in filter size and/or increased filter capacity, for example, increased dust holding capacity in the case of an air filter. The corrugated axial filter is formed by a plurality of parallel flow channels or flutes having alternately sealed ends, such that fluid entering an open end of a channel must pass through the filter media forming the wall of the channel and then exit the opposite open end of the adjacent channel.
Various problems have been encountered in corrugated axial filters, including in air filter applications. One of the problems is that the dust cake is not uniformly formed because of non-uniform flow across the filter media. This is objectionable because the filter media area cannot be fully utilized for high dust-holding capacity. Furthermore, such non-uniformity may actually reduce dust-holding capacity. Another problem is high flow restriction due to the large sealed area at the end of the channel or flute. Another problem is that the area of the channel or flute end is too big to be completely sealed, and hence leakage is common, and the filter may not be reliable for its purpose of primary filtration. Furthermore, the large sealing area is subject to high aerodynamic pushing force during flow, which force increases with time and can eventually open some sealed ends and cause the filter to malfunction. The sealed ends act like particle impactors. Large particles collect at such sealed ends and form dust cakes. The dust cakes grow and block other channel or flute open ends, ultimately resulting in filter clogging after relatively low dust loading.
The present invention addresses the above problems and improves overall performance. The invention enables use of a simple fold pattern, easy manufacturing steps, and enables a variety of structural configurations. Dust holding capacity is increased due to a more uniform dust flow field and maximum use of filter media surface. Optimized flow channels provide lower pressure drop. Significantly smaller sealing edges, instead of large open ends, use much less adhesive material and also reduce leakage possibilities. Geometrically more stable channels are provided which are harder to be compressed and thus provide greater structural integrity. Large inlet and outlet openings reduce filter clogging. A simple known folding method is utilized, instead of prior complicated folding patterns such as oblique folds requiring partial double layers and apex tip joint sealing. The invention enables efficient and economical manufacturing methods.